The price of a restored My Twinn doll varies.  The primary determinants of value are:

1. The face mold.  Some faces (like Ariel, Catherine, Rosemary, Emma, and many more) are common.  Other faces (like Clementine, Pearl, Kim, Tasha, Beth, and a few others) are rare and therefore raise the price of the doll.

2. Year of manufacture.  Denver-era dolls (2002 and earlier, based on original body tag) are made of higher quality materials and are more valuable.  The China re-pour heads are probably the least valuable in terms of the quality of materials...but that's where some rare faces can be found, so there's a tradeoff.

3. Skin tone.  The extremes of skin tone (very light or very dark) are more valuable than the middle range.

4. The cost of the original doll.  All of the factors, above, contribute to what I have to pay for a used doll.  This tends to be between $20 and $100.  If I pay more than $100 for a used doll, I probably intend to keep her in my collection.

5. The overall quality/success of the restoration and the price of the materials. Typical material prices include:

Monique wigs typically cost between $25 and $35
Custom wigs from Etsy (ZaZou, Doll of a Kind, etc.) cost between $25 and $60
Dollmore wigs cost between $25 and $35 

Acrylic eyes cost between $5 and $10
Lauscha glass eyes cost $35
Silicone eyes cost between $20 and $40
Hand Glass Craft D400 glass eyes cost $80

Eyelashes: $6

Outfits: $20-100

Despite all of these variables, I try to keep the cost of my restored dolls between $80 and $300.